Ejector and sealing means especially suitable for loose pieces in sand molding apparatus



Aug. 29, 1961 R. L. OLSON 2,997,755

EJECTOR AND SEALING MEANS ESPECIALLY SUITABLE FOR LOOSE PIECES IN SAND MOLDING APPARATUS 2 Sheets-Sheet 1 Filed Dec. 9, 1958 Richard L Olson Bi W/QEM 22w Aug. 29, 1961 2,997,755

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United States Patent C i 2,997,755 EJECTOR AND SEALING MEANS ESPECIALLY SUITABLE FOR LOOSE PIECES IN SAND MOLD- ING APPARATUS Richard L. Olson, 5739 S. Mozart St., Chicago 29, 111. Filed Dec. 9, 1958, Ser. No. 779,125 Claims. (Cl. 22-13) The present invention relates especially to novel means to assure separation of loosely contacting members liable to binding together but which must be positively separated during an operating cycle or other operation requiring separation, and more especially concerns ejector means which is also adapted to serve as a sealing medium.

As an example of an environment in which the problem of separability of confronting parts is encountered, core boxes are referred to which are extensively used in the foundry industry in the making of sand coresto be used in the casting of hollow metal articles. Due tothe necessary shape and configuration of the core it is often necessary to provide loose pieces which must be separable from the core box or mold assembly with the formed. sand core. If there is any sticking of the loose forming piece when the core box is opened so that the piece is moved relative to the soft, uncured sand core damage to the extent of possibly causing scrapping of the sand core results. In fact, in some instances scrap losses will run as high as 50% due to such sticking. At best, when such damage to the soft sand core occurs extensive patching may be required in order to save the core.

The reason for such sticking has usually been that sand grains become trapped in the relatively slidably opposing surfaces of the loose piece and the core box member or members and thus resist free separation of the piece relative to the core box members.

It is accordingly an important object of the present invention to provide improved means for exerting a positive ejecting force on opposing members which must be separated from an operating coaction requiring a faceto-face engagement of the members.

Another object of the invention is to provide an improved ejector device of non-metallic material and possessed of compressible characteristics attaining desirable compression loading for effecting a positive member separating ejector action between members that must be in close engagement at one time but must be positively separated at another time.

A further object of the invention is to provide a positive non-metallic ejector structure which also serves efficiently as a sealing medium.

Still another object of the invention is to provide improved means to prevent the sticking of loose pieces in blow-type core boxes.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of a preferred embodiment thereof taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a fragmentary perspective View of a core blowing machine, showing a core box embodying features of the present invention;

FIGURE 2 is a top plan view of the lower or drag portion of the core box;

FIGURE 3 is a separated assembly view of both the upper or cope and the lower or drag members of the core box;

FIGURE 4 is an enlarged fragmentary sectional detail view taken substantially on the line IV--'IV of FIGURE 3 but with the core box sections closed;

FIGURE 5 is a view similar to FIGURE *4 but show- Patented Aug. 29, 1961 ing the core box sections in a partially separated condition; and

FIGURE 6 is a fragmentary sectional view taken substantially on the line VI-VI of FIGURE 5.

Referring to FIGURE 1, a core box is shown including a lower or drag section 10 and an upper or cope section 11, the drag section being supported by a suitable table or conveyor 12 under a blow head or plate structure 13 of a core blowing machine including a ram and magazine structure 14. The cope half 11 of the core box may be raised and lowered relative to the lower or drag half 10 of the core box, or the lower half may be raised and lowered relative to the upper half, depending upon the preferred operation of the core blowing machine, upstanding centering pins 15 on the parting face of the drag section 10 registering with hushed sockets 17 opening from the parting face of the cope section "11.

Recessed in the parting face of the drag section 10 of the core box is a suitably contoured cavity 18 for forming substantially one-half of a sand core 19, the complementary contours for the remainder of the core 19 being provided in a molding .cavity 20 recessed in the parting face of the upper cope section 11 of the box (FIG. 3).

By way of example, the core 19 is for the hollow interior of a cast transmission case which requires that a flange or fin project from the wall of the inside of the casting. For this purpose, the core 19 must have a corresponding, complementary recess or slot 21 (FIGS. 4 and 5) opening therefrom at the proper place. It is customary to form such a slot in the core by means of a loose piece 22 provided with a flange fin 23 to provide the desired shape for the recess 21 in the core. To accommodate the piece 22 complementary opposing halfrecesses 24 and 25 are provided in respectively the drag section 10 and the cope section 11. In order to avoid build-up of sand between the opposing complementary surfaces of the piece 22 and the core box sections within the recesses 24 and 25, a reasonably close fit is preferred. However, due to the blowing pressure with which the sand is discharged into the core box cavity, there is a tendency for fine sand to work into the joints, including the joint surfaces which are in generally sliding interengagement and are angular to the parting face joint between the core box sections, thereby creating a binding or tendency to stick of the piece 22 when the core :box sections are separated.

In a customary procedure, the upper or cope section 11 of the core box is separated from the lower or drag section 10 when the core 19has been blown and is ready for curing so that the binder usually used in core sand will hold the sand particles solidly enough to permit handling the core after it is removed from the drag section 10 of the core box in which the core remains until it is cured. Accordingly, it is necessary for the piece 22 to remain with the drag section 10 and the uncured core 19. For this purpose, it is essential that the piece 22 separate positively from the cavity 25 in the cope section 11 so as to avoid breaking out of the portion of the core 19 which overlies the forming flange 23 of the loose piece 22. If the piece 22 sticks in the recess 25 of the cope section 11, it will cause the shaping flange 23 .to move with the piece 22 relative to the core 19 and thus displace the material on top of the forming flange and damage the core.

According to the present invention, positive ejection of the piece 22' from the recess 25 in the cope section 11 is eflfected by a non-metallic, compressible elastic member 27 preferably formed from a sponge type elastomeric material molded or otherwise permanently bonded within a suitable recess 28 in the face defining the recess 25 which opposes the face of the loose piece 22. Projecting from the body of the ejector member 27 is a flat crown pro ection 29 which is smaller across its root than the width of the recess 28 so that the projection 29 can compress into the body of the ejector 27 without pinching on the edges defining the recess 28. As best seen in FIGURES Sand 6, the projection 29 is to a substantial extent beyond the face of the member 11 opposing the loose piece 22 so that when the projection 29 is compressed into the elastic body 27 as best seen in FIGURE 4, it will develop substantial compressive force reacting toward the loose piece 22, but a metal-to-metal contact is nevertheless effected between the opposing faces of the piece 22 and the cope section 11 within the recess 25.

The best results have been obtained by making the ejector member from a compressible, cellular elastomer possessing a high degree of resiliency. While cellular rubber as such may be used, different types of synthetic resinous materials that are capable of being molded and set to a compressible, closed cell elastomer may be used. The material of the ejector 27 is conformed to the contour of the recess 28 and bonded to the walls defining such recess with such thorough adherence that during compression of the ejector member the body thereof will not separate from the wall surfaces of the recess. Thereby, sand or other foreign material will be positively prevented from entering alongside of or behind the ejector to disrupt the proper resilient functioning thereof, such as experienced with metal springs set in recesses into which sand or other foreign material can pack, but will be positively excluded.

In an advantageous structure, the material used for the ejector 27 is such as may be cured in situ by vulcanization or baking. Suitable natural or synthetic rubber, a plasticizer, a vulcanizing agent, and a gas-liberating agent capable upon the application of heat of liberating substantial quantities of gas and thereby swelling or expanding the elastomeric composition and producing a self-sustaining, resilient, elastic multi-closed-cell sponge rubber-like body very well suits the purpose. Of course, the material must be capable of withstanding adequately releasing and cleaning agents such as kerosene and the like.

For in situ curing of the ejector 27, a master plate having therein a recess conforming to the projection 29 'is matched with the recess 28 and a suitable quantity of the raw material for the ejector is confined within the chamber thus provided. The assembly is then placed in a curing oven and subjected to the proper temperature or vtemperatures for the proper length of time to effect expansion and curing of the material of the ejector. By having the surfaces within the recess 28 treated to as 'sure active bonding of the material of the ejector 27 thereto as an incident to the curing process, and by having the surfaces of the master plate opposing the recess 28 treated to assure non-adherence thereto of the material -of the ejector 27, the master plate will readily separate from the projection 29 and those portions of the body "of the ejector 27 extending between the root of the projection and the side edges defining the recess 28 while the ejector 27 remains permanently with the core box sec- -tion to which bonded.

shallower recess, or by varying the amount of material per unit area placed into a given size recess. In a typical installation, a compression factor of about 80 pounds per 'square inch has been found suitable. However, this can be varied for greater or less compression thrust, dependmg upon the amount of work to be done by the ejector. Another manner of predetermining the compression factor resides in the total area of opposition of the ejector to the opposing surface of the member to be forced into separation relative to the member carrying the ejector. For example, in the illustrated embodiment the ejector is in the form of a strip running at least almost as long as the length of the loose piece 22 and in this instance also having an angular leg running through a substantial portion of the width of the piece, clear of the particular forming flange 23 of the instant piece 22. For the same depth of ejector body a greater width per unit area would proportionately increase the compression loading.

Another valuable feature of the ejector 27 as shown resides in its function as a seal against blowing of sand across the horizontal joint between the loose piece 22 and the wall defining the recess 25 toward the generally vertical joint surfaces where the sliding fit between the loose piece and the cope section 11 may bind due to sand particles between the closely fitting opposing surfaces. While in the illustrated instance, the ejector 27 does not provide a complete seal, it could be readily extended endwise to provide such a complete seal. In any event, it serves sufliciently in its sealing function to preclude any appreciable blowing of sand into the sliding joint, which taken together with the positive ejection action assures at all times positive ejection of the piece 22 when the cope section is removed from the drag section of the core box and effective freedom from straining the core 19 in the vicinity of the forming flange 23, because the piece 22 is positively ejected relative to the cope section 11 so as to remain firmly seated in the recess 24 of the drag section 10 until the core has been cured and thus is substantially resistant to damage.

It will be understood that modifications and variations may be effected without departing from the scope of the invention as defined in the appended claims.

I claim as my invention:

1. In a core box assembly including a cope section and a drag section, a loose piece for maintaining a recess in a core formed in the assembled cope and drag sections, said sections having mating recesses therein within which said loose piece is closely seated in the assembly with a portion of the loose piece projecting into a cavity within which a sand core is to be formed in the cope and drag assembly, the mating recess in the cope section having a surface facing in the same direction as the parting face of the cope section, said surface having a recess therein, and a compressible non-metallic ejector bonded in said recess in said surface and normally projecting therefrom but compressed into said recess in said surface by seating of the loose piece in said matching recesses in the assembly and operative upon separating the cope section from the drug section to positively eject the loose piece from said matching recess in the cope section so that the loose piece will remain stationary with the drag section and a sand core that has been formed in said cavity and within which said projecting portion of the loose piece is embedded.

2. An assembly as defined in claim 1 wherein said e ector comprises a body of closed cell elastomeric material.

3. An assembly as defined in claim 1 wherein said recess in said surface is a groove running substantially across the matching recess of the cope section and said ejector comprises a closed cell elastomeric body seal for sealing the joint between the loose piece and said surface in the assembly against transportation of sand past the ejector-seal.

4. In a core box assembly including a cope section and a drag section having separable parting faces and defining a core blowing cavity therebetween, a loose piece having a seating portion and a projection, said sections having in the parting faces and opening into the cavity matching recesses within which said seating portion of the loose piece is firmly seated in the assembly with the projection extending into the cavity to form a recess in the blown core, and a combination sealing member and ejector comprising a compressible resilient strip mounted in the matching recess in the cope section and opposing the seating portion of the loose piece under compression and acting upon separation of the cope section from the drag section to positively eject the loose piece from the matching recess in the cope section so as to maintain the loose piece firmly seated in the matching recess in the drag section to remain therewith while the formed core is cured.

5. In a core box assembly including a cope section and a drag section relatively cavitated to provide a sand core forming cavity into which sand is adapted to be blown to form a core in the cavity, the parting face of at least the drug section having a recess opening also into the cavity, a loose piece having a seating portion conformably seating in said recess and also with a forming portion to project into cavity to form a recess in a core blown into the cavity, forming a recess in the surface of the cope section which opposes the seating portion of said loose piece in the assembly, said recess in the cope section having directly vulcanized and bonded therein a closed cell elastorneric ejector with a portion of the ejector projecting beyond said surface of the cope section, in the assembly of said loose piece in said recess in the drag section, and assembly of the cope section with the assembled drag section, said ejector being compressed against the loose piece, so that afiter blowing a sand core into the cavity, and thereafter separating the cope section from the drag section, there is positive separation of the loose piece relative to the cope section as effected by the ejector and the loose piece thereby remains with the drag section.

References Cited in the file of this patent UNITED STATES PATENTS 516,972 Henderson Mar. 20, 1894 554,380 Smethers Feb. 11, 1896 2,157,983 Glougie May 9, 1939 2,665,461 Rodgers Jan. 12, 1954 

